Hooray for you! I'm so excited your numbers are going up.
I'm going to interject with a hug .B.U.T here... Hcg numbers are NOT reliable in determining twins. These numbers basically tell whether the pg is healthy and progressing the way it should.They can "point" to twins, but since the numbers vary vastly from lady to lady and there is lots of crossover between singleton and twin numbers you can't go by that alone. It also depends on which chart you use, some go by dpo, others weeks and still others months...these also vary vastly.It is mostly used as a diagnostic tool that can determine if more testing is need....ie an u/s.
You were taking clomid though, right? That ups your chance of twins. Good luck at your ultrasound!!!